Re: [OSPF] [IPv6 SR] Regarding 128 bits IPv6 address in Segment List of SRH

"Stefano Previdi (sprevidi)" <sprevidi@cisco.com> Fri, 10 February 2017 09:30 UTC

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From: "Stefano Previdi (sprevidi)" <sprevidi@cisco.com>
To: "Acee Lindem (acee)" <acee@cisco.com>
Subject: Re: [OSPF] [IPv6 SR] Regarding 128 bits IPv6 address in Segment List of SRH
Thread-Topic: [OSPF] [IPv6 SR] Regarding 128 bits IPv6 address in Segment List of SRH
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Date: Fri, 10 Feb 2017 09:30:52 +0000
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the use of ll addresses in ospfv3 draft is a bug and should be fixed.

s.


> On Feb 10, 2017, at 12:41 AM, Acee Lindem (acee) <acee@cisco.com> wrote:
> 
> 
> 
> On 2/9/17, 5:48 PM, "OSPF on behalf of Brian E Carpenter"
> <ospf-bounces@ietf.org on behalf of brian.e.carpenter@gmail.com> wrote:
> 
>> Mark,
>> On 10/02/2017 08:26, Mark Smith wrote:
>>> On 10 Feb. 2017 03:02, "Veerendranatha Reddy Vallem" <
>>> veerendranatharv@huawei.com> wrote:
>> ...
>>>> If Link local address is Link local, how we can use this address in
>>>> SRH header, 
>>>> since IPv6 destination address should not be link local address as per
>>>> IPv6 protocol.
>>> 
>>> I'd be curious where you might have got that idea from.
>>> LL addresses are perfectly fine as destination addresses, including for
>>> application traffic. They're even preferred over global and ULA
>>> addresses
>>> by default when there is a choice from a set.
>> 
>> Right, but if an SR header is travelling off-link, which I think must
>> often
>> be the case, it would be doubleplus ungood to include a LL address, which
>> is
>> meaningless off-link. So probably using a LL address in SRH needs to be
>> strictly limited.
> 
> Agreed - even though the the link-local address is associated with the
> OSPFv3 router¹s adjacency, in the IPv6 SR header there is no indication of
> outgoing interface so the IPv6 packet cannot be forwarded unambiguously.
> Note that we have a similar restriction for OSPFv3 AS-External-LSA and
> NSSA-LSA forwarding address. From RFC 5340:
> 
> 
>   Forwarding address
>      A fully qualified IPv6 address (128 bits).  Included in the LSA if
>      and only if bit F has been set.  If included, data traffic for the
>      advertised destination will be forwarded to this address.  It MUST
>      NOT be set to the IPv6 Unspecified Address (0:0:0:0:0:0:0:0) or an
>      IPv6 Link-Local Address (Prefix FE80/10).  While OSPFv3 routes are
>      normally installed with link-local addresses, an OSPFv3
>      implementation advertising a forwarding address MUST advertise a
>      global IPv6 address.  This global IPv6 address may be the next-hop
>      gateway for an external prefix or may be obtained through some
>      other method (e.g., configuration).
> 
> 
> The OSPFv3 Segment Routing Extensions draft will be updated to correct
> this. 
> 
> Thanks,
> Acee
> 
> 
>> 
>>  Brian
>> 
>>> Many of the advantages of LLs for end-user applications would also
>>> apply to
>>> network applications such as SR.
>>> 
>>> "How to use IPv6 Link-Local Addresses in Applications"
>>> https://tools.ietf.org/html/draft-smith-ipv6-link-locals-apps-00
>>> 
>>> Regards,
>>> Mark.
>>> 
>>> 
>>> 
>>> If Adj-Sid is global ipv6 address, means we need to consider ³global
>>> ipv6 interface address² of the neighbor on the link?
>>> 
>>> 
>>> 
>>> Regards,
>>> 
>>> Veerendranath
>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
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>